1. Field of Invention
This invention relates to a frictionless and noisefree differential drive. With a noncontact engaging mechanism, the rider has on board driving and steering capability.
2. Description of Prior Art
So far, none of the foot-powered vehicles have multiple functions of steering, braking, driving forward, driving backward and free-running. This causes limitations in every aspect. For example, the skater needs to push against the ground and the dancer cannot slide across the stage with a pose. The sets strict restrictions in the performance.
The skateboard is a popular short-range transportation apparatus. The inventor has created several types of skateboards having foot-powered capability. The rider does not need to push against the ground. However, none of the skateboards have onboard single-foot driving, steering, braking, differential drive, twisting to skate and noiseless free-running capabilities. U.S. Pat. No. 4,411,442 issued to Rills (1983) discloses a curved toothed rachet gear rack which engages the curved pinion gear to impart rotational energy to the wheels. His ratchet gear rack is easily broken when the rider hits the stone in jumping. His ratchet mechanism drives forward only. His ratchet gear racks arc too noisy in driving. His curved pinion gears are too expensive to manufacture. Even in the free running mode, the ratchet mechanism makes a lot of noise and makes the rider uncomfortable to ride. The ratchet mechanism does not have the brake and driving backward functions. His invention uses the tilt of the board to change the direction. It makes the board unstable to stand on. His pedal doesn't have the combinatory functions of braking, driving and steering. U.S. Pat. No. 4,861,054 issued to Spital (1989) shows a pedal-powered skateboard which is too heavy for the rider to carry. Similar to the automobile transmission, his invention adopts many gears which are too expensive for a skateboard. His invention adopts the overrunning clutch which drives forward only. The crank mechanism uses reversible stroke motion. As the crank mechanism moves upward, it cannot drive the ratchet gear. Half of the working cycle is wasted. His invention has no brake. To steer his skateboard, the rider tilts the deck which is high above the ground. It is very dangerous to ride his skateboard. U.S. Pat. No. 3,399,906 issued to Portnoff (1968) showed a skateboard using the curved gear rack. It is too noisy to use. The skateboard has no steering capability and braking capability. U.S. Pat. No. 1,574,517 issued to Rohdiek (1926) showed a propelling mechanism having ratchet teeth or gear with a roller clutch. The ratchet teeth are too noisy. For a skateboard, the gear equipped with roller clutch mechanism is too large to be used. The board swivels such that the rider has difficulty standing on the board. His invention has no brake capability. The rider uses two hands to steer the vehicle. U.S. Pat. No. 4,181,319 issued to Hirbod (1980) shows a ski equipped with the crank mechanism but having no ratchet mechanism. His rubber gasket is to prevent the undesirable cross-movement. His rubber gasket doesn't have the multiple functions of my invention: the shock absorber, steering and recovering the wheels to straight forward position. His invention doesn't have the free-running capability. The rider stands on the pads with two feet continuously stepping on the pads upward and downward. There is no time for the rider to rest. The pedal doesn't have the steering capability. The rider cannot use the pedal to brake.
Furthermore, standing on the pedals and twisting the pedal, my skateboard can skate backward and forward. None of the prior art has the twisting capability to skate forward and backward.
The differential drive for a single continuous undivided drive axle is very important fundamental technology. U.S. Pat. No. 836,035 issued to Hendricks (1906) showed a continuous undivided axle with clutch mechanism thereby elinimating the expensive and intricate gearing and trusses employed with divided axles. The frictionless and noisefree differential drive has been the bottleneck of the skateboard technology. U.S. Pat. No. 2,246,191 issued to Schmitz (1941) shows a velocipede driving mechanism for a single wheel only, not for differential drive. My invention has the differential drive having engaging drive mechanism. The engaging mechanism replaces the ratchet and/or the gear mechanism used in the skateboard.
Furthermore, the U.S. Pat. No. 2,246,191 issued to Schmitz uses spring clip finger 20 in FIG. 2 to secure the two collar parts with the radial friction force. As stated in the U.S. Pat. No. 4,143,747 issued to Langieri, Jr., the spring clip finger is easily broken. So the coaster brake of Langieri, Jr. uses the eccentrically weighted driver of drum. However, the eccentrically wighted drum didn't solve the problem either. It caused the unbalance of the wheel and the safety problems of sudden lock of the wheel in high speed.
The key issue in the engaging mechanism is how to hold the engaging drum without friction and the failure of the mechanical parts.
To solve the above problems of the frictionless and noisefree grip of the engaging mechanism, my invention makes a lot of technological breakthroughs. In the first version, I change the radial frictional force to be the upper bounded axlewise gripping force. The engaging mechanism is filled with the grease. Therefore, there is less friction between the mechanical parts of the engaging mechanism. Furthermore, the gripper protects the spring from the moving part of the engaging mechanism so that the spring will not be broken. As the driving force exceeds the upper bounded axlewise force set by the spring, the gripper automatically releases the engaging drum. With the upper-bounded axlewise force, the engaging mechanism can work at high speed without the failure of the engaging mechanism.
In the second version, I make the fundamental breakthrough of the noncontact force. The contact mechanical force is replaced with the noncontact magnetic or electrical gripping force. The working principle of the noncontact gripping force is completely different from those of the mechanical frictional force. The noncontact engaging mechanism uses the minimum potential energy to hold the engaging drum and uses the rider's momentum to smooth the riding.
To run on a muddy or snowy road, the skateboard needs on-board manipulatory capibilities. The on-board manipulation includes on-board driving, on-board steering and on-board braking capabilities. U.S. Pat. No. 4,337,961 issued to Covert et al. (1982) disclosed an invention using eight wheels and four belts. His invention has no on-board manipulatory capability. His belt is not designed for the foot-powered skateboard and cannot be used on the foot-powered skateboard. U.S. Pat. No. 1,604,923 issued to Laurier (1926) shows auto tract device with the spring or rubber band enveloping the rollers. The spring or rubber band have to be deformed in steering. So the stretchable belt does't have the capacity to carry the heavy load. Even worse, the restoring force in spring or rubber makes the steering very difficult. These problems make his stretchable track impractical. U.S. Pat. No. 3,934,664 issued to Pohjola (1976) shows the endless track. The central portion of the endless track is nonstretchable. The central region cannot adjust its length and the track cannot envelop wheels having varying wheel pitch. Furthermore, his track blocks the passage of the transmission line. The rotation power cannot be transmitted from feet to wheels. So the skateboard has no foot-powered driving capability. Even worse, during steering, the track slides on the roller. The friction between the roller and the track is a serious problem.
In summary of the previous patents, none of them has the novel design of a crank mechanism with a silent ratchet mechanism having steering capability. A ratchet mechanism makes noise. Half of the energy and working cycle are wasted.
The foot-powered skateboard adopting the ratchet mechanism has no brake capability, no backward drive capability and/or no steering capability. The skateboard using the crank mechanism has no ratchet mechanism. The rider has no time to rest. The rider cannot use the pedal to steer. All the foot-powered skateboards heretofore known suffer from a number of disadvantages:
(a) The pedal doesn't have single-foot manipulatory capabilities of steering, driving and braking. During driving, the rider must use hands or feet to activate the other mechanisms to steer or to brake the skateboard. It is inconvenient and dangerous. PA1 (b) The skateboard doesn't have the backward driving capability, sideways driving capability, twisting to skate and brake capabilities. PA1 (c) The ratchet mechanism can drive the wheels to run forward only. The ratchet mechanism makes too much noise. The energy in half the working cycle is wasted. PA1 (d) It is dangerous to tilt the board in skating. PA1 (e) The ratchet mechanism is too complex to manufacture. The ratchet mechanism is dangerous to operate. The exposed gear rack is a threat to the safety of children. The ratchet mechanism is too large to port. PA1 (f) The gear is too heavy and it costs too much for a skateboard. PA1 (a) to provide a pair of skating shoe to the dancer that the dancer can sweep across the stage with poses. PA1 (b) to provide a short range transportation facility; PA1 (c) to provide a new apparatus for social dance activities. PA1 (d) to provide an apparatus for a new kind of atheletics.